FIELD OF THE INVENTION
The invention relates to a method for recycling metal parts contaminated by radioactive elements, in particular by .alpha.-emitters, in which a melt and a slag are formed from the metal parts and the slag is then separated from the melt.
When dismantling as well as when operating nuclear facilities, large amounts of contaminated metal, in particular iron-containing scrap, are produced and have to be recycled or disposed of. It is customary to subject the scrap to a melt decontamination. The radioactive elements which the scrap contains are, for example, .alpha.-emitters, such as uranium, thorium, transuranium elements and/or alkaline-earth metals.
A method which includes a melt decontamination is known from German Published, Non-Prosecuted Patent Application DE 33 18 377 Al. In that method, the contaminated metal is melted, and a slagging agent is added to the melt which is formed. A slag which floats on the melt is then formed. Radioactive elements (e.g. uranium, neptunium and plutonium), which caused the contamination of the metal parts, accumulate in the slag. Thus, while the concentration of those elements in the slag increases, their concentration in the melt decreases. That is to be attributed to the fact that the solubility of the elements in question is greater in the slag than in the melt. Decontamination of the melt is thus achieved. The slag is later drawn off from the surface of the melt. Its volume is small as compared to the total volume of the melt and the slag. It is only that small volume of slag which has to be taken to final storage. Consequently, only a relatively small final storage capacity is required. The metal melt, which has a volume that is significantly greater than the volume of the slag, is decontaminated and can therefore be reused. For example, shaped metal parts may be produced from decontaminated metal.
Although the elements which caused the contamination of the metal parts are substantially removed from the metal melt by using the known melt decontamination, a further increase in the degree of decontamination is nevertheless desirable.
Published French Patent Application 2 479 540 discloses a method for the disposal of radioactive waste in which component parts of the waste are oxidized.